Method and apparatus for producing curved panes having a two-level curving station

ABSTRACT

The invention relates to a production line for curved panes, in which the panes of glass are heated, brought in a horizontal position into a curving station where they are taken over by curving tools, and then finally conveyed into a quenching station, the stages of quenching and of entry of the glass into the curving station being at different heights.

This is a continuation of application Ser. No. 07/454,649, filed on Dec.21, 1989, now U.S. Pat. No. 5,069,704.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for the production of curved panesintended notably for automobile vehicles, according to which each sheetof glass is, in a first period, heated above its deformationtemperature, conducted into a curving station situated in thecontinuation of the furnace and in which the high temperature of theglass is maintained and then, after curving, is transferred into acooling station, for example a thermal quenching station.

2. Description of the Related Art

For producing automobile panes, notably fixed side panes, side windowpanes, rear panes or windscreens, it is necessary to shape a flat sheetof glass which is cut to the dimensions of the pane, and then to carryout lamination or, more frequently, tempering or toughening of thecurved pane in order to give greater safety to the passengers in thecase of fracture of the pane.

Many methods of curving, termed horizontal methods, are known, in whichthe glass sheet is heated above its softening point (500°-700° C.) in anelectric furnace, which it passes through conveyed, for example, by abed of motorized rollers. The heating furnace is followed by a curvingstation, in which the glass is shaped by specific curving tools and, forexample, in which the glass sheet is raised above the conveyor, andapplied against a curving mold, and then finally collected by a carriagecarrying a ring profiled in a manner corresponding to the final form ofthe curved pane. Thereafter, the carriage removes the glass sheet, forexample towards a quenching or tempering device or other cooling device.

In other cases, reserved almost exclusively for the manufacture oflaminated panes, the pair or pairs of glass sheets is deposited, at theentry of the furnace, onto a curving mold, on which it is directlyheated for a curving termed curving by collapse.

Without discussing in greater detail the technique of curving used, itshould be noted that the greater the accuracy required, and the morecomplex the shape, the slower the curving operation will be. To operatetoo rapidly leads to a risk of temporarily creating stresses higher thanthe strength of the glass and therefore of fracturing the glass.Furthermore, when the cooling step consists of a thermal quenching, forexample by blowing on cold air, it is essential for the pane to still beas hot as possible when it enters the tempering station.

For these reasons, the Applicant has chosen, in the present case, toinvestigate only those shaping methods according to which thetemperature of the glass remains virtually constant throughout thecurving operation. Constant temperature does not signify total absenceof heat exchange with the glass sheet, and moreover the speeds ofpassage of the glass sheets do not systemically guarantee perfectthermal equilibrium (and this in any case may not be desired, sincelocal overheating promotes folding at these points, for example). On theother hand, the heat exchanges remain of extremely small amplitude, inthat it is chosen to carry out the molding in a hot enclosure, thetemperature of which is close to that of the glass and not in the openair, where the glass initially at about 650° C. would undergo a veryconsiderable cooling, which would be detrimental to good shaping qualityand in particular to the quality of quenching.

From the foregoing considerations it is clear that it is absolutelynecessary to avoid abrupt and uncontrolled variations in temperature inthe curving station. Moreover, although it is relatively easy thermallyto insulate a closed enclosure, it is quite otherwise in the case of acurving station which, of necessity, comprises two entries-exits (forthe introduction and removal of the glass sheets and/or the framesmounted on a carriage transporting the curved glass). Lateral leakagesoccur via the conveyor which removes the glass sheets from the furnace.The conveyor is most commonly composed of rollers, the pinions of whichengage on chains arranged outside the hot enclosure in order to simplifythe adjustments and, in particular, to obtain reasonably long workinglives for the drive motors for these rollers, for which it is well knownthat it is virtually impossible to operate them continuously and in asatisfactory manner at a temperature in the vicinity of 650° C.

At the inlet side, that is to say at the furnace side, there is nopossibility of cold air entering, in view of the fact that the curvingstation is at the same temperature as the furnace, of which itconstitutes, in the limit, the extreme downstream element. The lateralleakages may, furthermore, be prevented to a great extent by appropriatefilling or stopping-up. On the other hand, and to the extent to whichthe production line is situated in a building not subject to flows ofair, the feed of cold air which takes place is virtually constant andcan therefore be compensated by appropriate heating. In contrast, it isquite otherwise in the case of the outlet from the curving station.

In fact, the opening must be sufficiently wide to enable a curved sheetof glass to pass through, or in certain cases with a height of more than20 centimeters and a width of approximately 1 m 50 cm if a rear pane isconsidered. Unless an extraordinarily high energy consumption can beaccepted, it is entirely unacceptable to leave an aperture of suchdimensions permanently open. And even if it were assumed that the energycost could be accepted, the special problem of the entry of cold airconsequent upon the blowing of cold air for quenching would not besolved, so that it is practically impossible to create relativelyisothermic conditions.

In reality, all the "hot" curving stations are equipped with an outletdoor with means for rapid opening and closing. Nevertheless, each timethis door is opened, a very considerable amount of cold air enters. In aplant with a high throughput rate, the instant at which the door opensto permit the exit of a glass sheet, the shaping of which has just beencompleted, may correspond to the quenching of the preceding glass sheetand the entry into the curving station of the succeeding glass sheet.The flow of cold air will therefore lick the rollers and, in,particular, will cool the succeeding glass sheet, which evidently isvery harmful to the latter.

To overcome this, it is known to line the door of the curving stationwith a hot air curtain, generated by burners situated in the curvingstation. A descending curtain of hot air has the disadvantage of pushingback the cold air penetrating into the station towards the conveyor andtherefore towards the succeeding glass sheets, whereas an ascendingcurtain of hot air must be emitted at a pressure sufficiently low so asnot to cause the lifting of the glass sheet which is passing through thehot air curtain. This systematic limitation to the permitted pressuredoes not allow complete compensation of the flow of cold air, so that itis necessary to provide precise synchronization of the movements of thedifferent glass sheets, in order that the arrival of the glass sheetshall be sufficiently late for homogenization of the temperature of thecurving station to take place between two glass sheets.

SUMMARY OF THE INVENTION

Accordingly, one object of this invention is to provide for a novelmethod of shaping glass sheets which minimizes the influence of thepenetration of cold air into the curving station, thereby making higherproduction rates possible. In the method according to this invention theglass sheet penetrates into the curving station in a substantiallyhorizontal direction at a storey defined as a lower storey and leavesthis curving station, still in a substantially horizontal direction, butat a storey defined as a higher storey, distinct from the lower storey.In the present invention, the term "storey" is used to indicate that thecurving station is seen as a succession of at least two superimposedchambers--but without walls defining the floor and the ceiling, certainelements being situated solely at a given storey (for example, theconveyor, which brings in the glass sheets from the furnace exit), orthe frame which removes the glass sheets after shaping), others such asthe glass sheets pass from one storey to the other.

In such a configuration, the cold air penetrates very much above thelevel of entry of the glass sheets, at a level close to the vault of thecurving station. Since the latter is equipped with heating resistorsdesigned for keeping an adequate temperature, the cold air is thenimmediately heated and does not disturb, to any great extent, a sheet ofglass conveyed to the lower level.

This effect is still further reinforced if, in accordance with apreferred embodiment of the invention, the entry door is lined with acurtain of hot air produced by means of heating resistors situatedbetween the lower level and the upper level. This hot air curtaincontributes to the heating of the cold air, but in particular deflectsthe path of this cold air by directing it towards the vault of thecurving station and the resistors which are situated there, so that notonly is the cold air warmed but furthermore it is diluted in the mass ofhot air of the curving station.

A further object of this invention is to provide for a novel method ofshaping glass sheets, capable, if desired, of operating in accordancewith the two-storey method described above. In fact, different meanshave been proposed for the application of the sheet glass against thecurving mold. In a first series of methods, exemplified notably by thePatent Application WO 85/05100, the glass sheet is raised and is pressedby a lower mold, composed of a peripheral ring raised through theconveyor.

In a second series of methods, to which the present invention moreespecially belongs, the application is carried out by forces of apneumatic nature. Thus, according to the theory of the Patent FR 2 085464, the glass sheet is sucked by a sub-pressure created at itsperiphery. It is also known, for example from the Patent EP 3 391, touse an upper section mold having a plane or very slightly arched surfaceperforated with numerous holes distributed over its entire area, whichcommunicate with a suction chamber in such a way that the glass sheetshall be sucked. Finally, it is also known, from European Patent EP 169770, to use a current of hot gas having a wide section, directedvertically upwards, which exerts upon the lower face of the glass sheetsufficient force to raise it and to apply it against the curving mold,the curvature of which it therefore hugs.

In the case of the curving methods in which the glass sheet is sucked bya peripheral sub-pressure, the curving mold is placed in anopen-bottomed chest, also termed skirt, connected to suction means, andthe contour of which is slightly larger than that of the glass sheet,cut out but not yet curved. The rise of the curving mold corresponds tothe rise which is desired to be imparted to the glass sheet, which is,in contrast, of dimensions slightly larger than those of the curvingmold.

On account of the presence of this projecting chest, the centering ofthe body of glass beneath the curving mold must be carried out withgreat precision, since the glass must not touch the walls of the chestand thus be marked by them, which would have the effect of a decreasedoptical quality, unacceptable for an automobile pane.

Another limit to this process lies in the shapes of pane which canthereby be obtained and in the practical impossibility of obtainingpanes of complex curvature, that is to say possessing in certainregions, most commonly localized near the edges of the pane, small radiiof curvature. It should be noted that this type of pane is frequentlyencountered, by reason of the need to integrate, into the glazed part ofautomobile vehicles, elements intended, for example, to improve thestreamlining of the vehicle, for example, a rear pane comprising a fold,which fulfills the function of an overlay or an immovable deflector,fixed to the frame of the lateral panes of the front doors of thevehicle. This limitation arises from the fact that the projection, on ahorizontal plane, of such a curved pane is of a dimension clearlysmaller than that of the flat sheet from which this pane originates. Asa consequence, the lateral leakage, that is to say the distance betweenthe edges of the glass sheet and the lateral walls of the chest,increases progressively as the shaping of the glass progresses, unless achest profile is chosen which corresponds exactly to the path of theedge of the glass sheet, a solution that would be difficult andimpractical, because then a new chest would be necessary for each changein manufacture and, moreover, in order to accurately determine this pathof the edge of the glass sheet, many tests might be necessary.

Thus, if a standardized chest is used, the operator finds himself in aparadoxical situation, in which the pneumatic force which acts at aportion of the glass sheet becomes smaller, the larger the curvaturewhich it is desired to give to this part.

It is known to carry out in these conditions, after a curving operationmaking use of pneumatic forces, a complimentary shaping by pressing bymeans of an annular counter-mold, which is placed beneath the uppercurving mold holding the glass sheet, and this counter mold may laterserve as a support for the glass sheet during its quenching. Theimproving of this complimentary curving, notably the optimization of thepressing duration, is made difficult by the lack of visibility due tothe presence of the chest. In practice, there will be a tendency tocontinue the pressing whereas the glass sheet has already virtuallyadopted the desired curvature by means of the curving mold and aninstantaneous pressing would be sufficient for completing the curve. Forthis reason, the curving cycle is extended. Furthermore, theopen-bottomed chest or skirt can damage the pressing elements duringintroduction.

A further object of this invention is to provide for an improved methodof curving a glass sheet which makes possible, in a simplified manner,the production of glass sheets with complex curvature, notably at theedges. Another subject of the invention is a device suitable forcarrying out the method according to this invention which makes itpossible to observe the path followed by the glass sheet during itsshaping.

In accordance with the method described in Patent FR 2 085 464, theglass sheet is preheated above the softening point of the glass and isconveyed, in a horizontal position, to the shaping cell, and is therelifted above the conveyor until it comes into contact with a curvingmold mounted in a suction chest. This method is characterized by the useof a suction chest composed of two elements movable relative to eachother, a lower element and an upper element carrying the upper mold, insuch a manner that a receiving carriage for the glass can penetratebetween the lower part of the chest and the upper part of the chest whenthe latter part is in a raised position.

Preferably, a large pneumatic force is applied during the transfer phaseof the glass sheet from the bed of rollers to the upper curving moldwhich corresponds to the period during which the depression chamber isbounded by the lower part of the suction chest--for the purpose ofchannelling the depression in an optimum manner in order to promote theascent. Then, while the glass sheet is applied against the upper curvingmold, the applied pneumatic force is reduced slightly in order toprevent those parts of the pane which come into contact with the curvingmold first, and therefore for the longest time,--that is to saygenerally the central part of the pane--from being marked by the mold,which would lead to optical defects.

The taking over of the glass sheet is achieved by a suction created atits periphery, the zone subjected to suction being bounded by the wallsof the lower part of the chest. These walls are preferably upright andthus constitute a vertical duct, the height of which is preferablyapproximately equal to the height of the free travel of the glass sheet,that is to say of the path which the glass sheet must follow beforecoming into bearing against the upper curving mold.

The upper part of the chest is preferably shaped, that is to say thatthe walls have a profile which corresponds approximately to the path ofthe edge of the glass sheet, in such a way as to maintain a constantdistance between the glass and the edge of the chest.

A suction chest is advantageously used, the upper part of which projectsa little beyond the curving mold, and at the limit, deflectors areplaced at the periphery of the curving mold at the necessary locations,strictly as a function of the requirements of curving, without takinginto account questions of bringing the glass sheet right up to the uppercurving molding. Moreover, the lowest level defined by these deflectorsor the walls of the upper part of the chest is preferably higher thanthe lowest level of the curving mold, or in other words this molddescends slightly lower than that part of the chest. Thus, the lateralleakage is of small dimensions at the end of the curving process, whichallows better management of the shaping in the most highly curved zones,generally at the edges of the pane.

When the upper part of the chest and the curving mold, which is integraltherewith, are raised, in accordance with this invention there remains afree zone between the lower part of the chest--which we shallhereinafter term "vertical duct"--and the upper part of the chest--whichwe shall again term "skirt". The height of this free zone is chosen insuch a way as to permit the introduction of a carriage carrying anannular skeleton, the outline of which corresponds essentially to thecurvature or rise which it is desired to give the glass. Since the skirtis preferably very short, it does not interfere with the entry of theskeleton, even for highly curved shapes. Furthermore, it permits perfectviewing of the glass sheet at the instant at which this sheet hugs thecontours of the curving mold.

The advantage of observation is certainly very great during the courseof industrial development, for example of a new set of equipment--set ofequipment is to be understood as comprising the upper mold and its chestas well as the quenching skeleton or skeletons and/or pressing skeletonor skeletons--notably for the purpose of defining the periods necessaryfor possible complementary pressing shapes. Observation is also veryuseful during manufacture, since it enables the work of the personnelresponsible for carrying out the adjustments at each change of type ofglass body to be guided, changes which occur several times per day.

For carrying out the method according to this invention, it isappropriate to use a suction chest composed of two distinct elements. Ina first example, the lower part of the chest or vertical duct may befixed and the upper part of the chest or skirt may be movable.

The use of a fixed vertical duct gives a particularly reliable referencebase, enabling the exact position of the glass sheet to be determinedwith great accuracy and enabling it to be recentered if necessary.Furthermore, since the skirt comes into bearing against the verticalduct in a low position, a very precise positioning in height of theupper curving mold is also achieved, which is certainly a gauge of thequality of shaping.

As indicated earlier, the invention is suitable particularly for themanufacture of highly curved panes, for which the quenching and pressingskeleton could not otherwise enter the suction chest. It is thereforeself-evident that the shaping process will usually be complimented orcompleted by a pressing step, although this does not in any way modifythe principle of this invention.

The method of shaping just described may be adapted to an installationcomprising an entry and an exit at different levels. But more generally,the principle of entry and of exit at different levels may be adapted toany of the shaping methods in a horizontal position, according to whichthe glass sheet is brought on a conveyor until it arrives at a positionaccurately underneath a curving mold, and is then raised by forces of apneumatic or mechanical type until it comes into bearing against thecurving mold, the curvature of which it hugs, if necessary with the helpof a supplementary pressing. In these methods--of which detailedexamples will be found in the aforementioned Patent Publications WO85/05100, FR 2 085 464, EP 3391 or EP 169 770--for the taking-over of asheet the curving mold is very near the feed conveyor for the glasssheets and therefore, at this instant, is situated at the lower storey.Once the glass sheet has been applied against the curving mold, it isknown according to conventional art to lift the curving mold slightly inorder to introduce a carriage carrying a frame which serves for theremoval of the glass sheets. But this frame also itself moves at thelower storey, at a level substantially equal to that of the feedconveyor. In contrast, in accordance with the present invention, thecurving mold is raised by a height considerably greater than the heightthat would be necessary solely for the purpose of permitting theintroduction of the carriage, and it is therefore in this high position,at the upper storey, that the removal is carried out. It should be notedthat the distance which the glass sheet travels from the instant atwhich it is applied to the curving mold is virtually immaterial from thepoint of view of the quality of shaping, whereas this obviously is notthe case for the distance travelled by the glass sheet alone for cominginto contact with the curving mold.

Another indirect advantage of this invention is that it makes possiblethe disposition, in the same alignment with the furnace, of the curvingstation and of the cooling station, notably quenching station. In fact,and unless provision is made for retracting the quenching chests, it isnot possible to remove a glass sheet directly out of the curving station(that is to say without causing it to undergo the entire shaping cycle)by passing it through the exit intended for correctly shaped panes, thisbeing due to the fact that panes of complex shape must be quenched inquenching blowing chests of such a shape that a flat sheet of glasscannot enter them. When the feed conveyor is at a different storey fromthe exit storey, it is possible, in contrast, to continue this conveyorby a device for removing and breaking up bodies of glass which are to bedirectly removed. This removal is carried out, for example, by a method,according to which the glass sheets are heated in a furnace, are broughtin a horizontal position into a curving station where they must be takenover by curving tools, then transported into a cooling, notablyquenching station, the defective bodies of glass being removed at theend of the curving station and being cracked for this purpose byatomization of a cold fluid, and then crushed.

The atomization of the cold fluid--for example water--takes placepreferably while the glass sheets are in movement on a dischargeconveyor, immediately before being crushed. In this way, even the glassvolumes of large dimensions can be reduced into fine pieces over a veryshort distance, which does not exceed for example 300 mm. This verysmall bulk enables the discharge system to be easily accommodatedaccording to this invention between a quenching station and a curvingstation disposed in alignment with the heating furnace for the glasssheets.

If necessary, the functioning of the discharge system may be triggeredin whole or in part by the detection of the presence of a defectivebody. The detection may thus govern the atomization of the cold fluidand the bringing into place of the crushing system, which is fitted inbetween two interventions, in order to not interfere with the movementsof the correctly curved glass sheets, or again may govern the startingup of the crushing means.

Such a detection is not, however, essential if the discharge systemaccording to this invention is advantageously applied to a productionline for curved and tempered glass sheets, for which the level of theglass sheets in the quenching station is different from the level of theglass sheets during their travel into the furnace. In this case, thedischarge system for the glass sheets, which by definition is located atthe level of the conveyor for the furnace which generally forms thelower level, is preferably made to operate continuously, since itsoperation cannot interfere with the treatment of the correctly curvedglass sheets, which are displaced at a higher level.

The discharge device for the defective bodies which is fitted to thecurving installation in a horizontal position comprising a heatingfurnace for the glass sheets equipped with a conveyor, a curving stationand a cooling station, notably quenching station, is situated on theaxis of the furnace, at the end of the curving station and fed by aconveyor continuing the conveyor of the furnace, and is composedessentially of at least one perforated pipe for atomizing cold fluid andmeans for crushing the glass. As the crushing means, there mayadvantageously be used a crushing mill or a hammering tool, such as aharrow moving vertically up and down. The crushing mill is, for example,formed of a rotationally driven roller provided with teeth. Ifnecessary, notably if the device is fitted to a production line, inwhich the levels of feed of the glass and quenching of the curved sheetsare not sufficiently widely spaced apart, the crushing means such as acrushing roller are mounted on an equipment which can be moved, forexample vertically, enabling these means to be retracted between twodefective bodies and a free passage to be left, for example, for thequenching frame. In this case, the discharge system is of necessityequipped with a detection device for detecting the presence of adefective body not taken over by the curving tools. This detectiondevice, which in particular may be of the type described in the PatentEP-A-217 708, then serves for instructing the start of atomization ofthe cold fluid and the raising of the movable equipment.

This discharge device is advantageously protected by a casing to preventany entry of cold air or it may closed by a curtain, for example ofasbestos, which the defective glass bodies lift to enter the dischargedevice (such a curtain is not possible for the exit of correctly shapedglass sheets, by reason of the risks of marking, which are quiteunimportant here, since the glass sheet is going to be converted intoscrap).

Accordingly, the present invention relates to a method of shaping glasssheets comprising the steps of: heating the glass sheets; transportingthe glass sheets, in a horizontal position, into a curving station,wherein the glass sheets are taken over by curving tools; and conveyingthe glass sheets into a cooling or quenching station; wherein the glasssheets enter and exit the curving station at storeys of differentheight.

The present invention also relates to a production line for producingcurved glass sheets comprising: a furnace for heating the glass sheet; acurving station; means for removing defective bodies of glass; and acooling station; wherein the furnace, the curving station, the means forremoving defective bodies of glass, and the cooling station aresuccessively disposed in the same alignment, the level of the glasssheets in the cooling station being different from the level of theglass sheets during their passage through the furnace and the curvingstation.

The present invention also relates to a method of curving a sheet ofglass comprising the steps of: preheating the glass sheet to atemperature above the softening point of the glass; conveying the glasssheets by way of a conveyor, in horizontal position, to a shaping cell;raising the glass sheet within the shaping cell, above the conveyoruntil the glass sheet comes into contact with a curving mold mounted ina suction glass, wherein the suction chest comprises two elements, thetwo elements being movable relative to each other, one of the twoelements being an upper element for carrying the curving mold so that acarriage for receiving the glass sheet can enter between the twoelements when the curving mold is in a raised position.

The present invention further relates to an apparatus for curving asheet of glass for producing automobile panes or the like, comprising: aheating furnace for heating the glass; a conveyor for transporting theglass; a curving cell; a curving mold; and a suction chest; wherein thesuction chest comprises a vertical duct and a skirt, the skirt beingmovable relative to the duct and integral with the curving mold.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will be readily obtained as the samebecomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 shows a layout for a curving-quenching installation, arranged inline, equipped with a system for removing defective bodies according tothis invention;

FIG. 2 shows an enlarged view of the discharge system for the defectivebodies according to this invention;

FIGS. 3 to 8 show the relative positions of the principal elementsrequired for carrying out the method according to the invention, duringthe successive steps of treatment of a glass sheet;

FIG. 9 shows a schematic view from below of a vertical duct, which canbe seen in FIGS. 3 to 8;

FIG. 10 shows a schematic view from below of the movable skirt, whichcan be seen in FIGS. 3 to 8;

FIG. 11 shows a view from the side of the vertical duct according toFIG. 9 and of the movable skirt according to FIG. 10 in a low position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The curving-quenching installation indicated systematically in FIG. 1comprises a furnace 3, for heating the glass sheets one by one. Theglass sheets are brought through the furnace by a conveyor 1, forexample possessing rollers 2, the reference level of which is indicatedby the broken line A. Following the furnace, the glass sheets, heated totheir tempering and curving temperature, enter the curving station 3.This curving station 3 comprises, for example, a tool-carrying assemblyequipped with a lifting system. This assembly is composed, for example,of an upper curving mold surrounded by a depression chest, connected toa suitable suction device, the curving mold being raised and loweredduring a curving cycle, for instance by means of chains 400, illustratedin FIG. 3 fixed to the tool-carrying assembly. Examples of curving toolsor molds and curving methods used in such methods are described, forexample, in Patent Applications EP 240 418 and EP 241 355.

A frame, for example a quenching frame, collects the sheets of glassafter they have been curved. This frame displaces along a level B,considerably higher than the level A which is the level of entry of theglass sheets into the curving station 3. It can therefore be seen thatthis installation comprises two distinct storeys. Once the glass sheethas been deposited on the quenching frame, it is conducted to thequenching station 4 after the door 5 has been opened. Also provided is aheating resistor 5(a) for lining the door (5) with a current of hot air.

This quenching station 4 comprises two blowing chests 6 and 7, mountedon a jack 8 and guided by slides 9, 10 in such a manner as to allow thechests to be separated for any maintenance. Ducts, not shown here, areprovided for the feed of blowing gas. The mean level of glass in thequenching station 4 is the level B; the expression "mean level" recallsthat the glass sheet is then curved to a more or less complex shape andthat in fact the two blowing chests have a shape conforming to thesurface of the curved glass sheet.

Referring now to the curving station 3, it will be noted that itcomprises, beneath the tool-carrying assembly, a conveyor 1 constitutinga continuation of the feed conveyor through the furnace. This conveyoris composed of rollers 2, resting on small rollers 11 and driven bychains 12, themselves driven by a motor 13, the assembly being supportedby a beam 14. All these elements, well known to the person skilled inthe art, have been indicated here only schematically in order to give anidea of the overall size of the various elements and of the difficultywhich results therefrom in laying out a discharge device for thedefective bodies of glass. In order to prevent a certain cooling down ofthe glass, which would decrease the effectiveness of the quenchingblowing, the quenching station must be situated as near as possible tothe curving station. For this reason, since the space available at thedownstream end 15 of the conveyor 1 is particularly small and, notably,is not sufficient to allow defective bodies of glass to be dropped thereas they are. This is why the installation is equipped with a dischargesystem, which has been indicated schematically here by the crushingroller 16, and which is shown in greater detail in FIG. 2.

In FIG. 2, the downstream end of the conveyor 1 with its last fourrollers including the extreme roller 15, can be seen, the rollers in thepresent case being hollow and of silica. The discharge system issurrounded by a casing 17, the bottom of which is provided with a trapdoor 18, permitting discharge into a scrap pit 19. This casing 17comprises an opening 20 for entry of a defective body 21, brought by theconveyor 1, and two apertures 22, 23. Opposite these apertures 22, 23are mounted nozzle pipes 24 and 25, extending across the entire width ofthe conveyor 1. The upper nozzle pipe 24 is fixed by a fixing lug 26 toa support plate 27, mounted by means of bolts 28 on an appendage to thelateral wall 29 of the curving station. The nozzle pipe 24 is equippedwith nozzles 30 for the atomization of a cold fluid, for example water.In a similar way, the lower nozzle pipe 25, equipped with atomizationnozzles 31, is fixed by a fixing lug 32 to a support 33. These twonozzle pipes are equipped with water feed ducts, not shown here. Theycontinuously discharge jets of atomized water 34, 35. Two nozzle pipesare used in the present case, but it is possible if necessary to operatethe discharge system with one single nozzle pipe.

When the defective body at its curving temperature passes between thejets 34, 35, it is entirely cracked by reason of the extremely intensethermal shock. Nevertheless, the pieces of glass remain positionedalongside one another like the elements of a reconstituted jigsawpuzzle. This is why the discharge device must be completed by a crushingdevice, composed in the present case of a crushing roller 16, equippedwith teeth 36 and rotationally driven by a device, not shown here. Incontact with the teeth 36, the cracked glass breaks up into numerousfragments, which fall into the pit 19 after passing through the trapdoor 18.

In a preferred embodiment, a scrap pit is not provided underneath thedischarge device but the scrap (cullet) is removed directly (andtogether with the atomized water) by an inclined vibrating conveyorbelt.

This inclined vibrating conveyor--or any other equivalentdevice--eliminates any need to stop for emptying.

The casing 17 occupies a very short length of the production line,preferably less than 300 mm, so that this assembly can be incorporatedwithout difficulty into the space available between the curving andquenching stations. Furthermore, since the discharge device is protectedby a casing, the atomization of water may be carried out continuously inan installation comprising two levels such as that shown in FIG. 1,without any risk of perturbing the treatment of the "standard" bodies ofglass.

If it is not desired to continuously operate the discharge device, forexample when the period of adjustment has passed, the line is equippedwith a detector 37, indicating, when applicable, the presence of adefective body of glass near the extreme downstream end 15. After adelay, if necessary, the detector 37 then serves for initiating one ormore of the operations such as the atomization, the rotation of thecrusher roller, and the starting up of the vibrating conveyor.

A method of curving according to the present invention comprises the useof a suction chest having two elements movable relative to each otherand an upper skirt-shaped element carrying the upper curving mold sothat a receiving carriage for the glass can come between the twoelements when the upper curving mold is in a raised position. Thevarious steps of the process according to this invention, are indicateddiagrammatically in FIGS. 3 to 9 and shall now be described. In thefurnace 300 the axis of which would be perpendicular to the plane of thedrawing, the glass sheets are heated one by one by being conveyedhorizontally on a bed of rotationally driven rollers. Following thefurnace, there is provided a curving cell 101, surrounded by refractorywalls 102 in order to maintain, in this curving cell, a temperature nearthat of the glass heated to 500°-700° C. The sheet of glass, brought onrollers 103 resting on bearings 104, is stopped beneath the uppercurving mold 105, which is attached by means of tension members 106 tothe suction chest 107. The suction chest 107 is connected to a chamber108 subject to partial vacuum, so that an ascending flow of air iscreated in the vicinity of the periphery of the upper mold 105.

Perpendicularly to the axis of the furnace, there are provided rails109, on which a carriage 110 carrying a skeleton 111 runs. These railspass between two quenching blowing chests 112, 113, and in contrast toconventional devices are situated at a level clearly higher than that ofthe rollers 103.

The glass sheet F is stopped and is correctly positioned beneath theupper curving mold, the latter is lowered into its low position (FIG. 3)in proximity to the surface of the sheet F. When it is desired tomanufacture a pane of especially complex shape, the dimensions of theplane glass sheet are clearly larger than those of the projection onto aplane of the glass sheet after it has been curved. Also in accordancewith this invention, the suction chest 107 is composed of two elementswhich are movable relative to each other, a vertical duct 115, forexample fixed, and a skirt 114 integral with the upper curving mold 105and movable by way of chains 400. This vertical duct 115 is of uprightsection. Its contour is similar to the contour of the glass sheet F inthe plane state, but projecting slightly beyond it in order to allow theperipheral suction of the glass sheet. The contour of the skirt itselffollows the trajectory of the glass sheet during its shaping. The skirttherefore decreases in section and preferably has a curved wall. Sincethe skirt 114 comes into action only indirectly during the first phaseof the operation, that is to say the phase of lifting during which thesuction must be most effectively channelled, it can be very short withan upper curving mold 105 which projects largely at the bottom.

As soon as the glass reaches the curving mold (FIG. 4), the suctionforce is preferably decreased slightly in order to prevent any risk ofdamage to the glass. At this instant, the upper mold 105--and thereforethe skirt 114--are raised into their upper position. The carriage 110 isthen brought towards the curving cell 101, after the door 116, whichseparates the curving cell 101 from the quenching cell, has been opened.

During this period, the glass sheet progressively hugs the contours ofthe curving mold. As can be seen in FIG. 5, this operation is not maskedby the contours of the chest 107, because the upper part of this chestis simply composed of the skirt 114, which being very short simply formsdeflectors around the upper mold 105 in order to channel the suction aircurrents. The associated skirt 114 and mold 105 are raised sufficientlyto enable the carriage 110 to be inserted, even if the skeleton 111 isof a particularly complex shape. The upper mold is then lowered again(FIG. 6) in order to deposit the glass sheet F on the skeleton 111. Thisdeposition may, if desired, be completed by pressing. In order tofacilitate this pressing, it is also preferable to provide a positioningof the pressing mold controlled by jacks, for example hydraulic jacks,which govern the movements of the skirt 114, whether in the ascending orin the descending direction. These jacks enable a constant pressure tobe assured without taking into account the weight of the upper mold andof the skirt. The mold 105 is again raised in order to release theskeleton (FIG. 7), which now conducts the sheet F between the blowingchests, where the quenching operation is carried out (FIG. 8).

For carrying out the method described above, a chest composed of theelements shown in FIGS. 9 and 10 may advantageously be used.

FIG. 9 concerns the lower part of the chest, here again termed verticalduct. The axis of the furnace is indicated by the broken line 120. Thispart of the chest is composed essentially of a plate 121, cut from ametal sheet and comprising notches 122, 123 for fixing it on suitablesupport means, for example of the bar type, so that the plate can slideand can be very rapidly replaced. To prevent any deformation in spite ofthe temperature of the cell and the large dimensions of the panes, thisplate is provided with stiffeners 124. The vertical duct 126, theaperture 127 of which corresponds, with slight excess dimensions, to thedimensions of the glass pane when flat, is fixed to this plate 121 byappropriate fixing means 125.

This part of the chest may be mounted fixed or vertically movablethrough a short distance of travel, of a height sufficient to allow anincorrectly sucked up glass sheet to be disengaged.

The upper part of the chest or skirt--still movable--is indicatedschematically in FIG. 10. The axis of the furnace has been indicatedhere by the broken line 130. On a plate 131, preferably of metal sheetequipped with stiffening elements 132, a plate 133 is fixed by gussetplates 137, which can be seen in FIG. 11.

These two plates support the skirt 134. Fixing is provided by means 136.The aperture 135 corresponds to the overall size of the pane aftershaping.

As indicated schematically in FIG. 11, where the vertical duct 126 andthe skirt 134 are shown in the position for sucking a glass sheet F',the travel of the skirt 134 is limited by a bearing of plastics material138, against which the plate 133 comes into bearing when the skirt is inits lower position.

The vertical duct 126--having a constant cross-section--preferablyserves as a support for centering means, for example pushers governed byjacks 200, as illustrated in FIG. 11, which pushers allow the glasssheet F' to be positioned very accurately at the center of the verticalduct 126. During this positioning, a slight suction and/or a slightvertical blowing by a current of hot air is created in the chest. Thepurpose of this is partly to relieve the rollers of the conveyor fromthe weight of the glass sheet F', so that there is no risk of this sheetbeing marked. It should be noted that, even when the vertical duct ismovable in height, it is in a position in close proximity to the planeof the rollers of the conveyor during a period much longer than thatavailable for the upper curving mold, and that it is therefore possibleto carry out a much more accurate positioning.

Obviously, numerous additional modifications, and variations of thepresent invention are possible in light of the above teachings. It istherefore to be understood that within the scope of the appended claims,the invention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A method of shaping glass sheets comprising thesteps of:heating said glass sheets; transporting said glass sheets at afirst level in a horizontal position into a curving station; curvingsaid glass sheets by way of curving tools in said curving station;moving said glass sheets, during said curving step, to a second levelwhich is substantially higher than said first level; continuouslyheating said curving station by way of heating means disposed betweensaid first and second levels; and conveying said glass sheets at saidsecond level to a cooling or quenching station such that a cold aircurrent which enters said curving station at said second level is heatedand deflected by heat from said heating means so as to not affect glasssheets at said first level.
 2. A production line for producing curvedglass sheets comprising:a furnace for heating the glass sheets; acurving station comprising means for curving the glass sheets; means forconveying said glass sheets, at a first level and in a horizontalposition, from said furnace to said curving station; means, in saidcurving station, for moving said glass sheets from said first level to asecond level of said curving station which is substantially higher thansaid first level; means for heating said curving station, said curvingstation heating means being disposed in said curving station betweensaid first and second levels; a cooling station for cooling said glasssheets; and means for conveying, at said second level, said glass sheetsfrom said curving station to said cooling station, wherein a cold aircurrent which enters said curving station at said second level is heatedand deflected by heat from said heating means so as to not affect glasssheets at said first level.
 3. An apparatus for curving a sheet of glassfor producing automobile panes or the like, comprising:a heating furnacefor heating the glass sheet; a curving station comprising a curving moldand a suction chest, said suction chest comprising a stationary verticalduct and a skirt which is integral with said curving mold, said skirtand integral curving mold being movable as a unit with respect to saidstationary duct; a conveying means for transporting the glass sheet fromthe furnace to the curving station; and a receiving carriage forreceiving a glass sheet which has been released from said curving moldand transporting said glass sheet from said curving station, whereinsaid skirt and integral curving mold are movable as a unit with respectto said stationary duct for permitting said receiving carriage to beintroduced therebetween for receiving the glass sheet released by thecurving mold.
 4. Apparatus according to claim 3, comprising centeringmeans for centering the glass sheet, said duct serving as a support forthe centering means.
 5. Apparatus according to claim 3, furthercomprising a bearing means for limiting ascending and descendingmovements of the skirt with respect to the duct, said bearing meansbeing positioned on the duct for contacting against the skirt when theskirt descends toward the duct.
 6. Apparatus according to claim 3,wherein said conveying means transports the glass sheet from the furnaceto the curving station at a first level, and said receiving carriagetransports said glass sheet from said curving station at a second levelwhich is different than said first level.